Certified Pool Operator Practice Test

At what hardness level does pool water typically begin to require dilution or replacement?

1. 400-600 ppm

2. 600-800 ppm

3. 800-1000 ppm

4. 1000-1200 ppm

The correct answer is: 400-600 ppm

Pool water generally requires dilution or replacement when the calcium hardness level reaches 400-600 ppm. This is because high levels of calcium can lead to cloudy water, scaling on pool surfaces, and decreased effectiveness of chlorine. Option B, ranging from 600-800 ppm, is incorrect as it is a higher range than the desired level. Likewise, option C of 800-1000 ppm is even higher and can lead to more severe issues. Option D, 1000-1200 ppm, is also incorrect as it is well above the recommended range and can cause damage to pool equipment. Therefore, option A of 400-600 ppm is the most appropriate level for pool water hardness and when dilution or replacement may be necessary.